Array substrate for in-plane switching mode liquid crystal display device including pixel and common electrodes on the same layer and method of manufacturing the same

ABSTRACT

An array substrate for an in-plane switching mode liquid crystal display device includes a substrate, a gate line along a first direction on the substrate, a data line along a second direction and crossing the gate line to define a pixel region, a common line on the substrate, a thin film transistor connected to the gate and data lines, a pixel electrode in the pixel region and connected to the thin film transistor, the pixel electrode including horizontal parts along the first direction, and a common electrode in the pixel region and connected to the common line, the common electrode including horizontal portions along the first direction, wherein the pixel electrode and the common electrode are formed on a same layer.

This application claims the benefit of Korean Patent Application No.2005-0133554, filed in Korea on Dec. 29, 2005, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to an array substrate for an in-plane switching (IPS)mode liquid crystal display (LCD) device and a method of manufacturingthe same.

2. Discussion of the Related Art

Liquid crystal display (“LCD”) devices are driven based onelectro-optical characteristics of a liquid crystal material. The liquidcrystal material has an intermediate state between a solid crystal andan isotropic liquid. The liquid crystal material is fluid like theisotropic liquid, and molecules of the liquid crystal material areregularly arranged like the solid crystal. An alignment direction of theliquid crystal molecules depends on the intensity or the direction of anelectric field applied to the liquid crystal molecules. Light passesthrough the LCD device along the alignment direction of the liquidcrystal molecules. By controlling the intensity or the direction of theelectric field, the alignment direction of the liquid crystal moleculeschanges, and images are displayed.

Active matrix liquid crystal display (“AMLCD”) devices, which includethin film transistors as switching devices for a plurality of pixels,have been widely used due to their high resolution and ability todisplay fast moving images.

Generally, an LCD device includes two substrates, which are spaced apartand facing each other, and a liquid crystal layer interposed between thetwo substrates. Each of the substrates includes an electrode. Theelectrodes from respective substrates face one the other. An electricfield is induced between the electrodes by applying a voltage to eachelectrode. The alignment direction of liquid crystal molecules changesin accordance with a variation in the intensity or the direction of theelectric field. The direction of the electric field is perpendicular tothe substrates. The LCD device has relatively high transmittance and alarge aperture ratio.

However, the LCD device has narrow viewing angles. To increase theviewing angles, various modes have been proposed. Among these modes, anIPS mode of the related art will be described with reference toaccompanying drawings.

FIG. 1 is a schematic cross-sectional view of an IPS mode LCD deviceaccording to the related art.

In FIG. 1, the IPS mode LCD device according to the related art includesa lower substrate 10 and an upper substrate 40, and a liquid crystallayer LC is interposed between the lower substrate 10 and the uppersubstrate 40.

A thin film transistor T, a common electrode 18 and a pixel electrode 30are formed at each pixel P on the lower substrate 10. The thin filmtransistor T includes a gate electrode 14, a semiconductor layer 22, andsource and drain electrodes 24 and 26. The semiconductor layer 22 isdisposed over the gate electrode 14 with a gate insulating layer 20therebetween. The source and drain electrodes 24 and 26 are formed onthe semiconductor layer 22 and are spaced apart from each other.

The common electrode 18 includes a plurality of portions, and the pixelelectrode 30 includes a plurality of parts. The portions of the commonelectrode 18 and the parts of the pixel electrode 30 are parallel to andspaced apart from each other on the lower substrate 10. The commonelectrode 18 may be formed of the same material and in the same layer asthe gate electrode 14. The pixel electrode 30 may be formed of the samematerial and in the same layer as the source and drain electrodes 24 and26.

Although not shown in the figure, a gate line is formed along a firstside of the pixel P, and a data line is formed along a second side ofthe pixel P perpendicular to the first side. A common line is furtherformed on the lower substrate 10. The common line provides the commonelectrode 18 with a voltage.

A black matrix 42 and a color filter layer 44 are formed on an innersurface of the upper substrate 40. The black matrix 42 is disposed overthe gate line, the data line and the thin film transistor T. The colorfilter layer 44 is disposed at the pixel P.

Liquid crystal molecules of the liquid crystal layer LC are driven by ahorizontal electric field 35 induced between the common electrode 18 andthe pixel electrodes 30.

The lower substrate 10 including the thin film transistor T, the commonelectrode 18 and the pixel electrode 30 may be referred to as an arraysubstrate. The upper substrate 40 including the black matrix 42 and thecolor filter layer 44 may be referred to as a color filter substrate.

FIG. 2 is a schematic plan view of an array substrate for an IPS modeLCD device according to the related art.

In FIG. 2, a gate line 12 is formed on a substrate 10, and a data line28 crosses the gate line 12 to define a pixel region P. A common line 16is parallel to and spaced apart from the gate line 12. The common line16 goes across the pixel region P. A thin film transistor T is formed ata crossing point of the gate line 12 and the data line 28. The thin filmtransistor T includes a gate electrode 14, a semiconductor layer 22, andsource and drain electrodes 24 and 26. The gate electrode 14 isconnected to the gate line 12. The semiconductor layer 22 is disposedover the gate electrode 14. The source and drain electrodes 24 and 26are disposed on the semiconductor layer 22 and are spaced apart fromeach other.

A common electrode 18 extends from the common line 16 and is formed inthe pixel region P. The common electrode 18 includes a plurality ofportions, which are parallel to and spaced apart from each other. Apixel electrode 30 is formed in the pixel region P. The pixel electrode30 includes a plurality of parts, which are parallel to and alternatewith the portions of the common electrode 18.

An IPS mode LCD device having the array substrate of the above-mentionedstructure has relatively wide viewing angles in a left-right directionwith respect to the device, but still has narrow viewing angles in anup-down direction or a diagonal direction with respect to the device.

To increase the viewing angles in the up-down or diagonal direction,another structure has been proposed.

FIG. 3 is a plan view of an array substrate for an IPS mode LCD deviceaccording to another embodiment of the related art.

In FIG. 3, a gate line 52 is formed along a first direction on asubstrate 50. A date line 66 is formed along a second direction. Thedata line 66 crosses the gate line 52 to define a pixel region P. A thinfilm transistor T is formed at a crossing point of the gate and datalines 52 and 66. A common electrode 56 and a pixel electrode 72 areformed in the pixel region P.

The thin film transistor T includes a gate electrode 54, an active layer60, a source electrode 62 and a drain electrode 64. The gate electrode54 is connected to the gate line 52. The active layer 60 is formed overthe gate electrode 54 with a gate insulating layer (not shown)therebetween. The source and drain electrodes 62 and 64 are spaced apartfrom each other over the active layer 60. The source electrode 62 isconnected to the data line 66.

The common electrode 56 is formed of the same material and in the samelayer as the gate line 52. The gate insulating layer (not shown) and apassivation layer (not shown) are formed between the common electrode 56and the pixel electrode 72 to prevent the pixel electrode 72 fromcontacting the common electrode 56. The pixel electrode 72 is formed ofa transparent conductive material to increase an aperture ratio. Thepixel electrode 72 may be formed of the same material and in the samelayer as the source and drain electrodes 62 and 64.

The common electrode 56 includes horizontal portions 56 a, a firstvertical portion 56 b and a second vertical portion 56 c. The horizontalportions 56 a are formed along the first direction and are spaced apartfrom each other. The first vertical portion 56 b is connected to oneends of the horizontal portions 56 a, and the second vertical portion 56c is connected to the other ends of the horizontal portions 56 a. Thepixel electrode 72 includes horizontal parts 72 a, a first vertical part72 b, and a second vertical part 72 c. The horizontal parts 72 a areformed along the first direction and alternate with the horizontalportions 56 a. The first vertical part 72 b is connected to one ends ofthe horizontal parts 72 a, and the second vertical part 72 c isconnected to the other ends of the horizontal parts 72 a.

Since the common electrode 56 and the pixel electrode 72 are arrangedalong the first direction, that is, substantially horizontally, theviewing angles are increased in the up-down direction. If the common andpixel electrodes 56 and 72 are inclined with a predetermined angle withrespect to the first direction, the viewing angles may be increased inthe diagonal direction.

However, the common electrode 56 and the pixel electrode 72 are formedin difference layers, and the common electrode 56 and the pixelelectrode 72 may be misaligned during respective processes. Themisalignment lowers image qualities of the device.

FIG. 4 is a cross-sectional view of an array substrate for an IPS modeLCD device according to another embodiment of the related art.

In FIG. 4, horizontal portions 56 a of a common electrode are formed ona substrate 50. A gate insulating layer 58 and a passivation layer 68are sequentially formed on the horizontal portions 56 a of the commonelectrode. Horizontal parts 72 a of a pixel electrode are formed on thepassivation layer 68. Each of the horizontal parts 72 a is disposedbetween adjacent horizontal portions 56 a.

After the horizontal portions 56 a are patterned through a mask process,the horizontal parts 72 a of the pixel electrode are patterned throughanother mask process. Each mask process includes a light-exposing step.A substrate is repeatedly exposed to light, moving with respect to amask because the mask is relatively very small in comparison with thesubstrate. Thus, during the light-exposing step, the mask may bemisaligned with the substrate.

As shown in FIG. 4, there is no misalignment in a first area NA.However, when a second area ANA is exposed to light in order to form thepixel electrode, the mask may be misaligned with the substrate 50. Adistance L1 between the common electrode and the pixel electrode in thefirst area NA is not equal to a distance L2 between the common electrodeand the pixel electrode. Accordingly, the quality of displayed images isnot uniform in some areas.

Moreover, since the common electrode is formed of an opaque material,the brightness of the device is relatively low.

SUMMARY

Accordingly, the present embodiments are directed to an in-planeswitching mode liquid crystal display device that substantially obviatesone or more problems due to limitations and disadvantages of the relatedart.

In a first aspect, an array substrate for an in-plane switching modeliquid crystal display device includes a substrate, a gate line along afirst direction on the substrate, a data line along a second directionand crossing the gate line to define a pixel region, a common line onthe substrate, a thin film transistor connected to the gate and datalines, and a pixel electrode in the pixel region and connected to thethin film transistor. The pixel electrode includes horizontal partsalong the first direction. A common electrode is provided in the pixelregion and connected to the common line. The common electrode includeshorizontal portions along the first direction. The pixel electrode andthe common electrode are formed on a same layer.

In a second aspect, a method of manufacturing an array substrate for anin-plane switching mode liquid crystal display device includes forming agate line along a first direction on a substrate, forming a data linealong a second direction, the data line crossing the gate line to definea pixel region, forming a common line on the substrate, forming a thinfilm transistor connected to the gate and data lines, and forming apixel electrode in the pixel region and connected to the thin filmtransistor. The pixel electrode includes horizontal parts of the firstdirection. A common electrode is formed in the pixel region andconnected to the common line. The common electrode includes horizontalportions. The pixel electrode is formed simultaneously with the commonelectrode.

In a third aspect, a method of manufacturing an array substrate for anin-plane switching mode liquid crystal display device includes forming agate line, a gate electrode and a common line on a substrate. The gateline extends along a first direction and is connected to the gate line.The common line is disposed between adjacent gate lines. An active layerand an ohmic contact layer are formed over the gate electrode. A dataline, a source electrode and a drain electrode are formed on the ohmiccontact layer. The data line extends along a second direction andcrosses the gate line to define a pixel region. The source electrode isconnected to the data line, and the drain electrode is spaced apart fromthe source electrode. A passivation layer is formed covering the dataline, the source electrode and the drain electrode. The passivationlayer includes a first contact hole exposing the drain electrode and atleast one second contact hole exposing the common line. A pixelelectrode and a common electrode are formed on the passivation layer,the pixel electrode including horizontal parts of the first direction,and the common electrode including horizontal portions.

In a fourth aspect, a method of manufacturing an array substrate for anin-plane switching mode liquid crystal display device includes forming agate line along a first direction on a substrate, forming a data linealong a second direction, the data line crossing the gate line to definea pixel region, forming a common line on the substrate, forming a thinfilm transistor connected to the gate and data lines, and forming apixel electrode in the pixel region and connected to the thin filmtransistor. The pixel electrode includes horizontal parts along thefirst direction. A common electrode is formed in the pixel region on thesame layer as the pixel electrode. The common electrode is connected tothe common line and includes horizontal portions along the firstdirection.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the embodiments and are incorporated in and constitutea part of this specification, illustrate embodiments of the disclosureand together with the description serve to explain the principles of thedisclosure. In the drawings:

FIG. 1 is a schematic cross-sectional view of an IPS mode LCD deviceaccording to the related art;

FIG. 2 is a schematic plan view of an array substrate for an IPS modeLCD device according to the related art;

FIG. 3 is a plan view of an array substrate for an IPS mode LCD deviceaccording to another embodiment of the related art;

FIG. 4 is a cross-sectional view of an array substrate for an IPS modeLCD device according to another embodiment of the related art;

FIG. 5 is a plan view of an array substrate for an IPS mode LCD deviceaccording to a first embodiment of the present invention;

FIGS. 6A to 6D and FIGS. 7A to 7D are cross-sectional views of an arraysubstrate in processes of manufacturing the same according to the firstembodiment;

FIG. 8 is a plan view of an array substrate for an IPS mode LCD deviceaccording to a second embodiment of the present invention; and

FIGS. 9A to 9D and FIGS. 10A to 10D illustrate an array substrate inprocesses of manufacturing the same according to the second embodiment.

FIG. 11 is a plan view of an array substrate for an IPS mode LCD deviceaccording to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings.

FIG. 5 is a plan view of an array substrate for an in-plane switching(IPS) mode liquid crystal display (LCD) device according to a firstembodiment of the present invention. In the first embodiment, a pixelelectrode and a common electrode are formed of a transparent conductivematerial and in a same layer. Parts of the pixel electrode and portionsof the common electrode are substantially parallel to a gate line.

In FIG. 5, gate lines 102 are formed along a first direction on asubstrate 100, and data lines 118 are formed along a second directioncrossing the first direction. The gate lines 102 and the data lines 118cross each other to define pixel regions P. A thin film transistor T isformed at each crossing point of the gate lines 102 and the data lines118. The thin film transistor T is connected to the gate and data lines102 and 118. The thin film transistor T includes a gate electrode 104,an active layer 110, a source electrode 114 and a drain electrode 116.

A common line 106 is formed on the substrate 100. The common line 106may be formed in the same layer as the gate line 102. The common line106 includes a portion of a loop shape at each pixel region P. Theportion is disposed along peripheries of the pixel region P, and theportion is substantially a square. The portions at adjacent pixelregions P are connected to each other along the first direction. Thecommon line 106 may have other shapes.

A common electrode 128 and a pixel electrode 126 are formed in eachpixel region P. The common electrode 128 is connected to the common line106, and the pixel electrode 126 is connected to the drain electrode116. The common electrode 128 is composed of a vertical portion 128 aand horizontal portions 128 b. The vertical portion 128 a is disposed ata first side of the pixel region P along the second direction, and thehorizontal portions 128 b extend from the vertical portion 128 a alongthe first direction. The pixel electrode 126 is composed of a verticalpart 126 a and horizontal parts 126 b. The vertical part 126 a isdisposed at a second side of the pixel region P, which is opposite tothe first side of the pixel region P, along the second direction, andthe horizontal parts 126 b extend from the vertical part 126 a along thefirst direction. The horizontal parts 126 b alternate with thehorizontal portions 128 b.

Here, the pixel electrode 126 and the common electrode 128 may be formedin the same layer. Therefore, although the mask for forming the pixelelectrode 126 and the common electrode 128 may be misaligned with thesubstrate 100, distances between the horizontal parts 126 b and thehorizontal portions 128 b are kept uniform.

Meanwhile, the pixel electrode 126 and the common electrode 128 may beformed of a transparent conductive material. The aperture ratio isincreased, and the brightness of the device is improved.

In addition, if the horizontal portions 128 b and the horizontal parts126 b are inclined with a predetermined angle with respect to the firstdirection, the viewing angles may be increased in a diagonal directionof the device.

A method of manufacturing an array substrate according to the firstembodiment will be described hereinafter with reference to accompanyingdrawings.

FIGS. 6A to 6D and FIGS. 7A to 7D are cross-sectional views of an arraysubstrate in processes of manufacturing the same according to the firstembodiment. FIGS. 6A to 6D correspond to the line VI-VI of FIG. 5. FIGS.7A to 7D correspond to the line VII-VII of FIG. 5.

In FIG. 6A and FIG. 7A, a switching region S and a pixel region P aredefined on a substrate 100. The pixel region P may include the switchingregion S. A gate line 102 of FIG. 5 and a gate electrode 104 are formedon the substrate 100. The gate line 102 of FIG. 5 extends along a firstdirection, and the gate electrode 104 is connected to the gate line 102of FIG. 5. A common line 106 is also formed on the substrate 100. Thecommon line 106 includes portions along peripheries of each pixel regionP. The portions of the common line 106 at adjacent pixel regions P areconnected to each other.

A gate insulating layer 108 is formed substantially on an entire surfaceof the substrate 100 including the gate line 102 of FIG. 5, the gateelectrode 104, and the common line 106 by depositing one selected froman inorganic insulating material group including silicon nitride(SiN_(X)) and silicon oxide (SiO₂).

An active layer 110 and an ohmic contact layer 112 are formed on thegate insulating layer 108 over the gate electrode 104 by depositingintrinsic amorphous silicon (a-Si:H) and impurity-doped amorphoussilicon (for example, n+a-Si:H) substantially on an entire surface ofthe substrate 100 including the gate insulating layer 108 and patterningthem.

In FIG. 6B and FIG. 7B, source and drain electrodes 114 and 116 areformed on the ohmic contact layer 112 by depositing a metallic materialsubstantially on an entire surface of the substrate 100 including theactive layer 110 and the ohmic contact layer 112 and then patterning it.The source and drain electrodes 114 and 116 are spaced apart from eachother. A data line 118 is formed simultaneously with the source anddrain electrodes 114 and 116. The data line 118 is connected to thesource electrode 114. Although not shown in the figure, the data line118 extends along a second direction and crosses the gate line 102 ofFIG. 5 to define the pixel region P. The metallic material may be one ormore selected from a conductive metallic group including aluminum (Al),an aluminum alloy such as aluminum neodymium (AiNd), chromium (Cr),tungsten (W), molybdenum (Mo), titanium (Ti) and molybdenum-tungsten(MoW).

Next, a part of the ohmic contact layer 112 is removed between thesource and drain electrodes 114 and 116, thereby exposing the activelayer 110.

In FIG. 6C and FIG. 7C, a passivation layer 120 is formed substantiallyon an entire surface of the substrate 100 including the source and drainelectrodes 114 and 116 by depositing one selected from an inorganicinsulating material group including silicon nitride (SiN_(X)) andsilicon oxide (SiO₂) or coating the substrate 100 with one or moreselected from an organic insulating material group includingbenzocyclobutene (BCB) and acrylic resin. The passivation layer 120 ispatterned to thereby form a drain contact hole 122 and common linecontact holes 124. The drain contact hole 122 exposes a part of thedrain electrode 116, and the common line contact holes 124 expose partsof the common line 106.

In FIG. 6D and FIG. 7D, a pixel electrode 126 and a common electrode 128are formed on the passivation layer 120 by depositing a transparentconductive material substantially on an entire surface of the substrate100 including the passivation layer 120 and then patterning it. Thetransparent conductive material is selected from a transparentconductive metallic group including indium tin oxide (ITO) and indiumzinc oxide (IZO). The pixel electrode 126 is connected to the drainelectrode 116 through the drain contact hole 122, and the commonelectrode 128 is connected to the common line 106 through the commonline contact holes 124.

As stated above, the pixel electrode 126 includes a vertical part 126 aand horizontal parts 126 b. The common electrode 128 includes a verticalportion 128 a and horizontal portions 128 b. The vertical part 126 a andthe vertical portion 128 a are disposed at opposite sides of the pixelregion P and overlap the portions of the common line 106. The verticalpart 126 a and the vertical portion 128 a are near by adjacent datalines 118, respectively. The horizontal parts 126 b extend from thevertical part 126 a, and the horizontal portions 128 b extend from thevertical portion 128 a.

The array substrate may be manufactured through the above-mentioned 4mask processes according to the first embodiment. In the firstembodiment, the pixel electrode and the common electrode aretransparent, and the brightness of the device is increased. Since theparts of the pixel electrode and the portions of the common electrodeare substantially parallel to the gate line, the viewing angles areimproved in an up-down direction with respect to the device.

In a second embodiment, a vertical portion, which is connected tohorizontal portions of a common electrode, and a vertical part, which isconnected to horizontal parts of a pixel electrode, are formed on adifferent layer from the horizontal portions and the horizontal parts.The horizontal portions and the horizontal parts overlap the verticalportion and the vertical part.

FIG. 8 is a plan view of an array substrate for an IPS mode LCD deviceaccording to a second embodiment of the present invention. In FIG. 8,gate lines 202 are formed along a first direction on a substrate 200,and data lines 220 are formed along a second direction crossing thefirst direction. The gate lines 202 and the data lines 220 cross eachother to define pixel regions P. A thin film transistor T is formed ateach crossing point of the gate lines 202 and the data lines 220. Thethin film transistor T is connected to the gate and data lines 202 and220. The thin film transistor T includes a gate electrode 204, an activelayer 212, a source electrode 216 and a drain electrode 218.

A common line 208 and a metallic pattern 206 are formed on the substrate200. The common line 208 and the metallic pattern 206 may be formed inthe same layer as the gate line 202. The common line 208 includes avertical portion of the second direction at each pixel region P. Themetallic pattern 206 and the vertical portion of the common line 208 areparallel to each other and disposed at opposite sides of each pixelregion P. The vertical portions of the common line 208 at adjacent pixelregions are connected to each other along the first direction. Themetallic patterns 206 at adjacent pixel regions P are disconnected toeach other.

A common electrode 232 and a pixel electrode 230 are formed in eachpixel region P. The common electrode 232 is connected to the common line208, and the pixel electrode 230 is connected to the drain electrode 218and the metallic pattern 206. The pixel electrode 230 and the commonelectrode 232 are formed on the same layer and are formed of atransparent conductive material.

More particularly, the common electrode 232 includes a plurality ofhorizontal portions. The pixel electrode 230 includes a plurality ofhorizontal parts. The horizontal portions alternate with the horizontalparts. The horizontal portions overlap the metallic pattern 206 and thevertical portion of the common line 208 and contact the vertical portionof the common line 208. The horizontal parts overlap the metallicpattern 206 and the vertical portion of the common line 208 and contactthe metallic pattern 206.

If the metallic pattern 206 and the vertical portion of the common line208 are formed on a same layer as the common electrode 232 and the pixelelectrode 230, to prevent a short circuit between the pixel electrode230 and the common electrode 232, there should exist areas horizontallyspaced between each horizontal portion and the metallic pattern 206 forcontacting the horizontal parts and between each horizontal part and thevertical portion of the common line 208 for contacting the horizontalportions. By the way, an electric field may be differently induced inthe areas from other areas. Since liquid crystal molecules may beirregularly arranged in the areas due to the different electric field,the areas may decrease the brightness of the device and the apertureratio.

However, in the second embodiment, the metallic pattern 206 and thevertical portion of the common line 208 are formed on a different layerfrom the pixel electrode 230 and the common electrode 232 and overlapthe horizontal portions of the common electrode 232 and the horizontalparts of the pixel electrode 230. There is no area horizontally spacedbetween each horizontal portion and the metallic pattern 206 and betweeneach horizontal part and the vertical portion of the common line 208.Accordingly, the short circuit can be prevented between the pixelelectrode 230 and the common electrode 232, and the aperture ratio andthe brightness of the device may be improved.

A method of manufacturing an array substrate according to the secondembodiment will be described hereinafter with reference to accompanyingdrawings.

FIGS. 9A to 9D and FIGS. 10A to 10D illustrate an array substrate inprocesses of manufacturing the same according to the second embodiment.FIGS. 9A to 9D are cross-sectional views corresponding to the line IX-IXof FIG. 8. FIGS. 10A to 10D are cross-sectional views corresponding tothe line X-X of FIG. 8.

In FIG. 9A and FIG. 10A, a switching region S and a pixel region P aredefined on a substrate 200. The pixel region P may include the switchingregion S. A gate line 202 of FIG. 8 and a gate electrode 204 are formedon the substrate 200. The gate line 202 of FIG. 8 extends along a firstdirection, and the gate electrode 204 is connected to the gate line 202of FIG. 8. A metallic pattern 206 and a common line 208 are also formedin the pixel region P on the substrate 200. The common line 208 includesa vertical portion disposed at a first side of the pixel region P. Themetallic pattern 206 is disposed at a second side of the pixel region Popposite to the first side. Although not shown in the figures, themetallic pattern 206 and the vertical portion of the common line 208extend along a second direction crossing the first direction. Thevertical portion of the common line 208 is connected to those atadjacent pixel regions P.

A gate insulating layer 210 is formed substantially on an entire surfaceof the substrate 200 including the gate line 202, the gate electrode204, the metallic pattern 206 and the common line 208 by depositing oneselected from an inorganic insulating material group including siliconnitride (SiN_(X)) and silicon oxide (SiO₂).

An active layer 212 and an ohmic contact layer 214 are formed on thegate insulating layer 210 over the gate electrode 204 by depositingintrinsic amorphous silicon (a-Si:H) and impurity-doped amorphoussilicon (for example, n+a-Si:H) substantially on an entire surface ofthe substrate 200 including the gate insulating layer 210 and patterningthem.

In FIG. 9B and FIG. 10B, source and drain electrodes 216 and 218 areformed on the ohmic contact layer 214 by depositing a metallic materialsubstantially on an entire surface of the substrate 200 including theactive layer 212 and the ohmic contact layer 214 and then patterning it.The source and drain electrodes 216 and 218 are spaced apart from eachother. A data line 220 is formed simultaneously with the source anddrain electrodes 216 and 218. The data line 220 is connected to thesource electrode 216. Although not shown in the figures, the data line220 extends along the second direction and crosses the gate line 202 ofFIG. 8 to define the pixel region P. The metallic material may be one ormore selected from a conductive metallic group including aluminum (Al),an aluminum alloy such as aluminum neodymium (AlNd), chromium (Cr),tungsten (W), molybdenum (Mo), titanium (Ti) and molybdenum-tungsten(MoW).

Next, a part of the ohmic contact layer 214 is removed between thesource and drain electrodes 216 and 218, thereby exposing the activelayer 212.

In FIG. 9C and FIG. 10C, a passivation layer 222 is formed substantiallyon an entire surface of the substrate 200 including the source and drainelectrodes 216 and 218 by depositing one selected from an inorganicinsulating material group including silicon nitride (SiN_(X)) andsilicon oxide (SiO₂) or coating the substrate 200 with one or moreselected from an organic insulating material group includingbenzocyclobutene (BCB) and acrylic resin. The passivation layer 222 ispatterned to thereby form a first contact hole 224, second contact holes226 and third contact holes 228. The first contact hole 224 exposes apart of the drain electrode 218, the second contact holes 226 exposeparts of the metallic pattern 206, and the third contact holes 228expose parts of the common line 208.

In FIG. 9D and FIG. 10D, a pixel electrode 230 and a common electrode232 are formed on the passivation layer 222 by depositing a transparentconductive material substantially on an entire surface of the substrate200 including the passivation layer 222 and then patterning it. Thetransparent conductive material is selected from a transparentconductive metallic group including indium tin oxide (ITO) and indiumzinc oxide (IZO). The pixel electrode 230 is connected to the drainelectrode 218 through the first contact hole 224 and is connected to themetallic pattern 206 through the second contact holes 226. The commonelectrode 232 is connected to the common line 208 through the thirdcontact holes 228.

As stated above, the pixel electrode 230 includes horizontal partsextending along the first direction and parallel to the gate line 202 ofFIG. 8. The common electrode 232 includes horizontal portions extendingalong the first direction and parallel to the gate line 202 of FIG. 8.The horizontal parts of the pixel electrode 230 alternate with thehorizontal portions of the common electrode 232. The horizontal parts ofthe pixel electrode 230 overlap the metallic pattern 206 and the commonline 208. The horizontal portions of the common electrode 232 overlapthe metallic pattern 206 and the common line 208. The horizontal partsof the pixel electrode 230 contact the metallic pattern 206 through thesecond contact holes 226, respectively. The horizontal portions of thecommon electrode 232 contact the common line 208 through the thirdcontact holes 228, respectively.

In the second embodiment, since there is no area horizontally spacedbetween the common electrode and the metallic pattern and between thepixel electrode and the common line, the aperture ratio is increased,and the brightness of the device is improved.

To prevent disclination in a displayed image, an array substrateaccording to a third embodiment will be illustrated in FIG. 11. FIG. 11is a plan view of an array substrate for an IPS mode LCD deviceaccording to the third embodiment of the present invention.

In FIG. 11, gate lines 202 are formed along a first direction on asubstrate 200, and data lines 220 are formed along a second directioncrossing the first direction. The gate lines 202 and the data lines 220cross each other to define pixel regions P. A thin film transistor T isformed at each crossing point of the gate lines 202 and the data lines220. The thin film transistor T is connected to the gate and data lines202 and 220. The thin film transistor T includes a gate electrode 204,an active layer 212, a source electrode 216 and a drain electrode 218.

A common line 208 and a metallic pattern 206 are formed on the substrate200. The common line 208 and the metallic pattern 206 may be formed inthe same layer as the gate line 202. The common line 208 includes avertical portion of the second direction at each pixel region P. Themetallic pattern 206 and the vertical portion of the common line 208 areparallel to each other and disposed at opposite sides of each pixelregion P between adjacent gate lines 202. The vertical portions of thecommon line 208 at adjacent pixel regions are connected to each otheralong the first direction. The metallic patterns 206 at adjacent pixelregions P are disconnected to each other.

A common electrode 232 and a pixel electrode 230 are formed in eachpixel region P. The common electrode 232 is connected to the common line208, and the pixel electrode 230 is connected to the drain electrode 218and the metallic pattern 206. The pixel electrode 230 and the commonelectrode 232 are formed on the same layer and are formed of atransparent conductive material.

More particularly, the common electrode 232 includes a plurality ofhorizontal portions. The pixel electrode 230 includes a plurality ofhorizontal parts. The horizontal portions alternate with the horizontalparts. The horizontal portions overlap the metallic pattern 206 and thevertical portion of the common line 208 and contact the vertical portionof the common line 208. The horizontal parts overlap the metallicpattern 206 and the vertical portion of the common line 208 and contactthe metallic pattern 206.

The common electrode 232 further includes protrusions DP at a first endof a first side of each horizontal portion and at a second end of asecond side of each horizontal portion, wherein the first end isopposite to the second end. The pixel electrode 230 further includesprotrusions DP at a first end of a first side of each horizontal partand at a second end of a second side of each horizontal part, whereinthe first end is opposite to the second end. The protrusions DP of thecommon electrode 232 and the pixel electrode 230 may have a triangleshape. The protrusions DP of the common electrode 232 and the pixelelectrode 230 control electric fields such that the electric fields maybe regularly induced around areas where the common electrode 232 and thepixel electrode 230 meet the metallic pattern 206 and the common line208. Therefore, the disclination in the displayed image can be preventeddue to the protrusions DP.

In the present invention, the common electrode and the pixel electrodeare transparent. In addition, the common and pixel electrodes overlapthe metallic pattern and the common line, and aperture areas areincreased. Therefore, the aperture ratio is increased, and thebrightness is improved.

Meanwhile, the disclination in the displayed image can be prevented dueto the protrusions DP of the common and pixel electrodes. The quality ofthe image is improved.

Moreover, the pixel electrode and the common electrode are substantiallyparallel to the gate line, the viewing angles are improved in an up-downdirection with respect to the device.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice of the present invention without departing from the spirit orscope of the invention. Thus, it is intended that the present inventioncover the modifications and variations of this invention provided theycome within the scope of the appended claims and their equivalents.

What is claimed is:
 1. An array substrate for an in-plane switching mode liquid crystal display device, comprising: a substrate; a gate line along a first direction on the substrate; a data line along a second direction and crossing the gate line to define a pixel region; a common line on the substrate; a thin film transistor connected to the gate and data lines; a pixel electrode in the pixel region and connected to the thin film transistor, the pixel electrode including horizontal parts along the first direction; a common electrode in the pixel region and connected to the common line, the common electrode including horizontal portions along the first direction; and a metallic pattern of the second direction on the substrate, wherein the metallic pattern contacts the horizontal parts and is disposed directly on and contacts the substrate, wherein the pixel electrode and the common electrode are formed on a same layer, wherein the pixel electrode further includes a portion directly connected to one of the horizontal parts, wherein the portion overlaps and contacts a drain electrode of the thin film transistor through a contact hole, wherein the portion overlaps the gate line.
 2. The array substrate according to claim 1, wherein the pixel electrode and the common electrode are formed of a transparent conductive material.
 3. The array substrate according to claim 1, wherein the horizontal portions alternate with the horizontal parts.
 4. The array substrate according to claim 1, wherein the common line further includes a vertical portion of the second direction, wherein the metallic pattern and the vertical portion are disposed at opposite sides of the pixel region.
 5. The array substrate according to claim 4, wherein the metallic pattern and the common line are formed on a same layer as the gate line.
 6. The array substrate according to claim 5, wherein the metallic pattern overlaps the horizontal portions and the horizontal parts, and the vertical portion of the common line overlaps the horizontal portions and the horizontal parts.
 7. The array substrate according to claim 6, wherein each of the horizontal portions and the horizontal parts further includes protrusions at a first end of a first side and at a second end of a second side, wherein the first end is opposite to the second end.
 8. The array substrate according to claim 7, wherein the protrusions substantially have a triangle shape.
 9. A method of manufacturing an array substrate for an in-plane switching mode liquid crystal display device, comprising: forming a gate line along a first direction on a substrate; forming a data line along a second direction, the data line crossing the gate line to define a pixel region; forming a common line on the substrate; forming a thin film transistor connected to the gate and data lines; forming a pixel electrode in the pixel region and connected to the thin film transistor, the pixel electrode including horizontal parts along the first direction; forming a common electrode in the pixel region on the same layer as the pixel electrode, the common electrode connected to the common line, the common electrode including horizontal portions along the first direction; and forming a metallic pattern of the second direction on the substrate, wherein the metallic pattern contacts the horizontal parts and is disposed directly on and contacts the substrate, wherein the pixel electrode further includes a portion directly connected to one of the horizontal parts, wherein the extended portion overlaps and contacts a drain electrode of the thin film transistor through a contact hole, wherein the portion overlaps the gate line. 